Biological and chemotherapeutic compounds are investigated for their ability to control infectious diseases in experimental animals. Biologicals include hyperimmune sera, globulins of human origin, bacterins, vaccines, antibiotics and antiviral agents. Products are tested in experimentally infected animals. Toxoplasmosis - Squirrel monkeys Saimiri sciureus are extremely susceptible to infection with Toxoplasma gondii. Oral inoculation with a suspension of chronically infected mouse brains produces an acute fatal disease in 8 to 10 days. In the Group B streptococcal studies penicillin was administered either prophylactically to pregnant rhesus monkeys two hours before delivery, or therapeutically to the newborns three hours after Group B strertococci inoculation. All newborns in the prophylaxis group died as a result of their infection while the mortality rate with postinoculation therapy was 40 percent.